Wireless communication devices comprise phones, computers, intelligent machines, or some other apparatus with a wireless transceiver. Wireless communication networks include base stations, distributed antenna systems, or some other type of wireless access point to exchange wireless signals with the wireless communication devices. The wireless communication devices and the wireless communication networks exchange electromagnetic signals over the air to support services like mobile Internet access, audio/video streaming, user data messaging, and the like.
The wireless communication networks use increasingly sophisticated antenna systems. In a simple antenna system, a single antenna in the wireless communication network transmits to a single antenna in the wireless communication device. In another antenna system, four antennas in the wireless communication network transmit to two antennas in the wireless communication device. In yet another antenna system, sixteen antennas in the wireless communication network transmit to four antennas in the wireless communication device.
There are various technologies to allocate the antennas to data streams and wireless communication devices. Using transmission diversity, the same data streams are simultaneously transmitted over separate antennas. Using spatial multiplexing, different data streams are transmitted over different antennas—perhaps to the same wireless communication device.
Multiple Input Multiple Output (MIMO) technologies allocate antennas to data streams and user devices. With Single-User MIMO (SU-MIMO), a single wireless communication device may use one or more network antennas at a given time. With Multiple-User MIMO (MU-MIMO), multiple wireless communication devices may share the same antenna at the same time. MIMO systems transfer multiple data streams (called layers) to the same wireless communication device. Thus, MIMO systems associate combinations of data streams, antennas, and wireless communication devices to perform both transmit diversity and spatial multiplexing.
Beamforming technologies use advanced amplification and phasing to control the direction and shape of the energy field propagating toward the target wireless communication device. The energy field near the wireless communication device is protected and enhanced, while the energy field away from the user device is intentionally destroyed with artificial interference. Effective beamforming typically requires feedback from the wireless communication device, such as its location and received signal quality. The feedback is used to direct the proper amount of energy in the proper direction.
The wireless communication networks and the wireless communication devices use the feedback to control transmit diversity, spatial multiplexing, MIMO, and beamforming. In a common feedback technique, reference signals are inserted into the wireless signals at expected times and frequencies by the wireless communication network. This pattern of time and frequency for the reference signals varies by the type of wireless transmission, and a given time/frequency pattern is referred to as an Antenna Port. The wireless communication device receives and processes the reference signals based on their current Antenna Port to generate their feedback for the wireless communication network. The feedback may indicate a channel quality, MIMO rank, or a precoding matrix indicator.
In Long Term Evolution (LTE) networks, some of the Antenna Ports transmit reference signals in an omnidirectional manner across an entire wireless sector or radio coverage area. Omnidirectional reference signals are often inserted in control signaling portions of the Antenna Port, since the control signaling is often transmitted in an omnidirectional manner. In the LTE networks, other Antenna Ports transmit other reference signals in a beam-formed manner along with beam-formed user data. Thus, the wireless communication device receives both omnidirectional reference signals and beam-formed reference signals.
The allocation of network antennas to a wireless communication device and its data streams is referred to as a network antenna configuration. In LTE, the network antenna configurations are called Transmission Modes (TMs). The network antenna configurations include various parameters for transmit diversity, spatial multiplexing, MIMO, and/or beamforming. The wireless communication networks select their network antenna configurations for individual wireless communication devices based on their device feedback. In LTE, the eNodeB selects the TMs for the wireless communication devices based on their channel quality feedback.
Unfortunately, the wireless communication devices do not effectively process reference signals to control the antenna configurations used by the wireless communication networks. In particular, LTE User Equipment does not process the omnidirectional reference signals and the beam-formed reference signals to direct the eNodeBs to switch from beamforming transmission modes to omnidirectional transmission modes.